quarkusio/quarkus · error · IllegalArgumentException

The given type is a type variable: " + requiredType

Error message

The given type is a type variable: " + requiredType

What it means

ArcContainerImpl.getBeans() rejects TypeVariable required types with IllegalArgumentException. The CDI spec requires the given type in BeanManager.getBeans() to be a concrete type; a type variable (e.g. T) carries no resolvable information. Arc fails fast instead of returning an empty/meaningless set.

Source

Thrown at independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/ArcContainerImpl.java:608

    @SuppressWarnings("unchecked")
    private <T> InjectableBean<T> getBean(Type requiredType, Annotation... qualifiers) {
        if (qualifiers == null || qualifiers.length == 0) {
            qualifiers = new Annotation[] { Default.Literal.INSTANCE };
        } else {
            registeredQualifiers.verify(qualifiers);
        }
        Resolvable resolvable = new Resolvable(requiredType, qualifiers);
        Set<InjectableBean<?>> resolvedBeans = resolved.getValue(resolvable);
        if (resolvedBeans.isEmpty()) {
            scanRemovedBeans(resolvable);
        }
        return resolvedBeans.size() != 1 ? null : (InjectableBean<T>) resolvedBeans.iterator().next();
    }

    Set<Bean<?>> getBeans(Type requiredType, Annotation... qualifiers) {
        if (requiredType instanceof TypeVariable) {
            throw new IllegalArgumentException("The given type is a type variable: " + requiredType);
        }
        if (qualifiers == null || qualifiers.length == 0) {
            qualifiers = new Annotation[] { Default.Literal.INSTANCE };
        } else {
            registeredQualifiers.verify(qualifiers);
        }
        // This method does not cache the results
        return Set.of(getMatchingBeans(new Resolvable(requiredType, qualifiers)).toArray(new Bean<?>[] {}));
    }

    Set<Bean<?>> getBeans(String name) {
        // This method does not cache the results
        return new HashSet<>(getMatchingBeans(name));
    }

    boolean isScope(Class<? extends Annotation> annotationType) {
        if (annotationType.isAnnotationPresent(Scope.class) || annotationType.isAnnotationPresent(NormalScope.class)) {
            return true;

View on GitHub (pinned to e1c734241f)

Solutions

1. Pass the concrete resolved type (e.g. new ParameterizedType with actual type arguments, or the raw class) instead of the TypeVariable
2. Capture the generic type via an anonymous subclass (TypeLiteral<T>() {}) and pass its type
3. Add a runtime guard in your helper rejecting TypeVariable inputs before calling getBeans

Example fix

// before
<T> void lookup() {
    container.getBeans(/* T is a TypeVariable */ currentType);
}

// after
Type type = new TypeLiteral<List<String>>() {}.getType();
container.getBeans(type, Any.Literal.INSTANCE);

if (requiredType instanceof TypeVariable) {
    throw new IllegalArgumentException("Resolve to a concrete type first: " + requiredType);
}
Set<Bean<?>> beans = Arc.container().getBeans(requiredType, qualifiers);

boolean isConcrete(Type t) {
    return !(t instanceof TypeVariable)
        && !(t instanceof WildcardType)
        && !(t instanceof GenericArrayType);
}

try {
    beans = container.getBeans(type, quals);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("type variable")) {
        beans = container.getBeans(rawType(type), quals); // fallback to raw type
    } else throw e;
}

When it happens

Trigger: Calling beanManager.getBeans(someTypeVariable, qualifiers) or Arc.container().instance(...)/select(...) where the passed java.lang.reflect.Type is a TypeVariable instance, typically obtained from a generic method parameter or field.getGenericType() on a generic class.

Common situations: Writing generic helper/utility code that does programmatic lookup with T; reflection-based frameworks passing getGenericType() results; generifying a previously concrete lookup after a refactor.

Related errors

• Event#select(Class<U>, Annotation...) cannot be used with ty
• Unable to determine if the '${unsecuredMethod}' method shoul
• Producer method return type is a parameterized type with a t
• InterceptionProxy parameter must be a parameterized type: ${
• Producer field type is a parameterized type with a type vari

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/4026b078bca3e41d. Report an issue: GitHub.